There is an image forming apparatus having a function of forming an image on a paper by a decoloring toner or a normal toner and a function of decolorizing an image by the decoloring toner formed on the paper. Such an image forming apparatus realizes a function of forming an image on a paper fed from a cassette and a function of heating the paper fed from the cassette to decolorize the paper by switching operation modes.
If a decoloring processing is stopped during execution, there is a case where an undecolored paper remains in the cassette. If an image forming processing is executed while the undecolored paper remains in the cassette, there is a problem that the image forming apparatus can print an image on the undecolored paper.